ANALOGUES 



tions : nicotinic acid, 2 x lo-^ to i x io~® ; methyl nicotinate, 

 37 X io~® to 2 X io~* ; nicotinamide, 2 x io~^ to i X io~® ; 

 nicotinamide methiodide, o-8 X ro"* to o-6 x lo-^ ; nicotinic acid 

 diethylamide, 0-3 X lO"* to 0-4 X lo"^ ; pyridine-/3-sulphonic acid, 

 1 X io~^ to more than 0-3 X io~^ ; pyridine-j8-suIphonamide, 

 27 X io~* to I X io~^ ; pyridine-j8-sulphonic acid diethylamide, 

 dilution uncertain ; 6-methylnicotinamide, less than o-6 X io~^ to 

 0-5 X io~^ ; methyl picolinate, less than 1-2 X io~^ to 4-4 x io~^ ; 

 nicotine, i-6 X io~^ to 0-5 X io~^ ; thiazole-5-carboxylic acid, 

 1-6 X io~* to 2 X 10-2 ; 2 : 6-dimethylnicotinamide, greater than 

 3-6 X io~^; 2-acetylnicotinic acid, greater than 1-6 x IQ-^ ; pyrazine- 

 monocarboxylic acid, greater than i-i X io~^ ; pyrazine-dicarboxylic 

 acid, greater than i-6 x lo-^. Many of these results are at variance" 

 with those obtained by other workers, most of whom have found, for 

 instance, that pyridine-j3-sulphonic acid and its amide cannot replace 

 nicotinic acid for micro-organisms. 



Thiazole-5-carboxylic acid amide did not replace nicotinic acid in 

 the nutrition of Pr. vulgaris ^6 or S. aureus,^'' but partially neutralised 

 the growth-stimulating effect of nicotinamide on the latter. Thiazole- 

 5-sulphonic acid in large amounts could replace nicotinic acid or the 

 amide for S. aureus. 



1:2:5: 6-Tetrahydronicotinic acid (gervacine) had a similar 

 action to nicotinic acid both on S. aureus and Pr. vulgaris, dehydrogena- 

 tion occurring very readily. Hexahydronicotinic acid was also utilised 

 by both organisms, but its effect was not immediate, dehydrogenation 

 apparently taking place with more difficulty than with the tetrahydro 

 compound.28 i-Methyl-tetrahydronicotinic acid (arecaidine) had no 

 growth-stimulating action. Tetrahydronicotinic acid did not increase 

 the oxygen uptake when added to pig's kidney or liver pulp. 



Most esters of nicotinic acid proved to be only slightly active 

 when tested on L. arabinosus.^^ Nipecotic acid had only o-oi % of 

 the activity of nicotinic acid towards this organism.^ A substance 

 isolated from wheat bran was as active as nicotinic acid in blacktongue 

 and in nicotinic acid deficiency in chicks,^* but stimulated the growth 

 of L. arahinosus only after hydrolysis with dilute alkali ; ^^ its pro- 

 perties suggested that it might be an ester. 



Substances Antagonistic to Nicotinic Acid 



Although according to E. F. Moller, pyridine-jS-sulphonic acid and 

 its amide may have a slight stimulating action on the growth of Pr. 

 vulgaris and S. aureus at relatively high dilutions and in the absence 

 of nicotinic acid or amide, other workers have found that they inhibit 

 the growth of these organisms . In presence of nicotinic acid or amide ^® 



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